<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">

function sunmin(){
	this.a = 5;
	this.b = 10;
};
sunmin.prototype = {
	'mm':function(){
		alert(this.a + this.b)
	},
	'nn':function(){
		alert(2);
	}
}

function licuan(){
	sunmin.call(this);
};

licuan.prototype = new sunmin();
/*
licuan.prototype.mm = sunmin.prototype.mm;
*/
new licuan().mm();

</script>
</body>
</html>